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Class Malacostraca - crabs, shrimps, lobsters Class Maxillopoda - ostracods, barnacles, copepods Class Branchiopoda - brine shrimp, tadpole shrimp Class.

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Presentation on theme: "Class Malacostraca - crabs, shrimps, lobsters Class Maxillopoda - ostracods, barnacles, copepods Class Branchiopoda - brine shrimp, tadpole shrimp Class."— Presentation transcript:

1 Class Malacostraca - crabs, shrimps, lobsters Class Maxillopoda - ostracods, barnacles, copepods Class Branchiopoda - brine shrimp, tadpole shrimp Class Remipedia - small cave-dwellers; basal lineage Class Cephalocarida - small benthic detritivores; basal SubPhylum Crustacea

2 Class Malacostraca SuperOrder Peracarida - carapace reduced in size - unique endites called oostegites (brood pouch, or marsupium) - direct development, which helped colonize land: bypass a planktonic larval stage, mother broods young & releases fully developed juveniles Order Mysida (opossum shrimp) Order Isopoda (isopods)  made it onto land Order Amphipoda (amphipods)

3 Class Malacostraca SuperOrder Peracarida Order Mysida (opposum shrimp) - well developed carapace covering head+thorax segments - pelagic, intertidal, or burrowing - often form benthic “swarms,” which are small clouds of tiny shrimp that hide among urchin spines for protection brood pouch where young develop

4 Class Malacostraca SuperOrder Peracarida Order Isopoda >10,000 species - no carapace: you can see each segment from above - one lineage successfully colonized dry land: the pill bugs - pereopods are very structurally variable - pleopods used in gas exchange Cirolana

5 rock louse kelp isopod

6 Class Malacostraca SuperOrder Peracarida Order Amphipoda8,000 species - no carapace - includes semi-terrestrial “beach hoppers” - thoracic gills are epipods, extensions of pereopods

7 Decapods typically brood their larvae to a well developed, large-eyed zoea larva capable of fast swimming and active behaviors, which can help larvae migrate in & out of estuaries After several molts, the final megalopa larva is produced, which looks very much like the adult - except in crabs, the abdomen is not yet tucked under the thorax Decapod Larvae crab zoea stomatopod (mantis shrimp) megalopa

8 Class Malacostraca - crabs, shrimps, lobsters Class Maxillopoda - ostracods, barnacles, copepods Class Branchiopoda - brine shrimp, tadpole shrimp Class Remipedia - small cave-dwellers; basal lineage Class Cephalocarida - small benthic detritivores; basal SubPhylum Crustacea

9 barnacles, copepods, ostracods Class Maxillopoda Head (5 segments) Thorax (6) Abdomen (4) - usually biramous limbs; no abdominal appendages - mostly small; reduced abdomen, missing some legs Subclasses: Thecostraca (barnacles) Copepoda Ostracoda 26,000 spp. free-living (acorn, gooseneck) parasitic on crustaceans

10 Class Maxillopoda: SubClass Thecostraca Free-living barnacles Parasitic Rhizocephalans - hermaphrodites- separate sexes - carapace produces shell- carapace lost - suspension feeders- endoparasites w/ interna and externa Capitulum Cirri Peduncle Scutum Tergum Externa Rootlets of ramifying body

11 - in adult barnacles, the appendages on the thorax (= thoracic legs, or cirri) are similar in appearance to tentacles of filter-feeding worms and crinoids (to come later) - used to filter feed: scutum and tergum plates open in response to water current, cirri extended up into water, then rapidly retracted inside shell over and over again

12 Antennule Antenna Mandible Naupliar eye Nauplius Larval Stage antennules, antennae, mandibles; no segmentation; single eye - successive molts: remaining head, thoracic appendages

13 Unique feature of barnacles: non-feeding cyprid larval stage which follows the nauplius stage - has a bivalved shell, and swims using antennae - in free-living barnacles, cyprid glues its head onto the first suitable hard surface it encounters Cyprid Larvae Cyprid attaching, cementing itself head-first to substrate become cirri of adult

14 - cephalic “shield” - keep single naupliar eye - primary consumer of phytoplankton - tiny; swim by flicking antennae Class Maxillopoda: SubClass Copepoda - 8,500 spp. Caudal rami Ovisac (clump of embryos) articulation point (attachment of thorax to abdomen) Antennule Antenna Naupliar eye

15 Class Maxillopoda: SubClass Copepoda - 8,500 spp. In males, 1 st antennae and 5 th thorax limb may be specially modified for “mate guarding” behaviors - males locate, grab and ride around holding a virgin female before her terminal (final) molt - this way, they ensure they are the male who will fertilize her eggs when she molts, and is then ready to mate

16 Class Maxillopoda: SubClass Ostracoda - 6,600 spp. - bivalved carapace (how many independent origins of a bivalved shell have we seen now??..) - reduced segmentation; body not split into thorax + abdomen - 5 head appendages thoracic appendages, including male copulatory limb-- fewest limbs of any crustacean - many are bioluminescent, using light flashes in complex mating rituals - swim using antennae

17 Class Malacostraca - Crabs, shrimps, lobsters Class Maxillopoda - Ostracods, barnacles, copepods Class Branchiopoda - Brine shrimp, tadpole shrimp Class Remipedia - small cave-dwellers; basal lineage Class Cephalocarida - small benthic detritivores; basal SubPhylum Crustacea

18 Class Branchiopoda Notostracans: tadpole shrimpAnostracans: fairy shrimp Artemia, brine shrimp no carapace telson carapace caudal ramus often inhabit freshwater vernal pools (temporary)

19 Sow bugs (terrestrial isopods) are most successful group - direct development cut ties to the sea Crustaceans on Land Land crabs must still return to the ocean to spawn Insects – molecular evidence indicates the most successful animal lineage evolved from a crustacean ancestor

20 Regier et al. 2010, Nature Analysis of 62 genes redefined arthropod relationships (1) Insects are nested within the “Crustacea”, which is therefore a paraphyletic group! New name, “Pancrustacea”, refers to crustaceans + insects

21 Regier et al. 2010, Nature (1) Insects are nested within the “Crustacea”, which is therefore a paraphyletic group! 2) Maxillopoda not a true group - barnacles, copepods & ostracods do not form a clade - despite sharing the same “formula” for body segments, these are all unrelated groups

22 Regier et al. 2010, Nature Insects are nested within the “crustacea”, which is therefore a paraphyletic group! 2) Maxillopoda not a true group 2a – barnacles are sister to Malacostraca (crabs, etc) 2b – copepods are sister to (Malacostraca + barnacles) 2c – ostracods are basal to rest of Crustacea

23 Tardigrades Onychophorans Arthropods Ecdysozoa Priapulids Kinorhynchs Loriciferans Nematodes Nematomorphs - clade Ecdysozoa was named in 1997 from an analysis of 18S ribosomal RNA gene - members all molt to grow, controlled by hormone ecdysone

24 - microscopic 8-legged “water bears” from semi-aquatic habitats prone to drying out (e.g. moss) - display extreme cryptobiosis when environments dry out: the ability to enter a state of suspended animation, with no metabolism or apparent ageing, until conditions improve - 4 pairs of unjointed legs - uncalcified cuticle lines parts of gut - main cavity = hemocoel; no gills, respire across wet body wall Phylum Tardigrada - “water bears” 3 Orders, 10 Families ~ 800 species

25 Cryptobiosis in Tardigrades During environmental stress, legs are pulled and body coated in a double-walled cuticular envelope, forming a cyst Then, a single-walled tun state develops, where metabolism is undetectable and individuals can survive long periods of dessication (= dryness) Tuns have survived… - up to 10 years without water - complete vacuum, long periods with no oxygen - temperatures near absolute zero: 8 hr at -272°C !! - toxic liquids (ether, 100% alcohol) Allows tardigrades to persist in an unstable ecological niche

26 stylet used to punch holes in plants or algae; then tardigrade sucks out cytoplsm mostly feed on plants, algae convergent evolution: very similar to the single tooth and method of feeding in sacoglossan sea slugs (my group, the herbivores)

27 Tardigrades Onychophorans Arthropods Ecdysozoa Priapulids Kinorhynchs Loriciferans Nematodes Nematomorphs clade Cycloneuralia – brain forms a loop around esophagus – anterior end = introvert, which can be withdrawn into body Cycloneuralia

28 Tardigrades Onychophorans Arthropods Ecdysozoa Priapulids Kinorhynchs Loriciferans Nematodes Nematomorphs clade Cephalorhyncha – spiny collar of scalids around the introvert Cephalorhyncha

29 Phylum Nematoda ~25,000 species - body round in cross-section, but no circular muscles; longitudinal muscles let them thrash around to move - covered in cuticle, shed in 4 molts during juvenile growth  allows survival in hostile environments - extensions of muscles called muscle arms branch out to contact neurons, instead of other way ‘round like most animals - unique excretory system featuring renette cells; no circulatory structures Includes model organism for developmental biology, C. elegans

30 Phylum Nematoda Ecological importance: - tremendously abundant decomposers per ml of coastal mud - 90,000 per rotting apple - 9 billion per acre of soil Medical importance: - cuticle allows them to resist immune system, function as endoparasites (endo = living inside the host’s body) - parasitic forms cause diseases including river blindness, elephantiasis, trichinosis

31 Nematomorphs – “ horsehair worms” - long thin body encased in well-developed cuticle - over 1 meter long, less than 1 mm wide - no apparent segmentation - all growth accomplished by larvae, which are parasites in arthropod hosts - gut, but no mouth; nutrients are absorbed from insect host across body wall, taken up by gut tissue ~320 species

32 Priapulids - benthic marine “worms” - introvert with hooked spines - complete gut, protonephridia for excretion - no circulatory system - thin cuticle surrounds body - loricate larva has special cuticle that’s shed at metamorphosis 18 species Introvert Trunk rings Caudal appendages

33 Phylum Kinorhyncha - all marine; interstitial = live between grains of mud or sand - body with 13 segments: head, neck, and 11-segment trunk - no cilia; crawl by extending head, locking spines in place - head = introvert; can retract into neck - ring of backward-facing spines (scalids) used to lock body in place when crawling  convergent evolution with how annelids use chetae to dig - well-developed cuticle - no larval stage! ~ 180 species

34 Phylum Kinorhyncha

35 Phylum Loricifera - all marine; only discovered in 1983! - body tiny ( 10,000 cells) - head with piercing stylets around mouth - head, neck + thorax retract into abdomen - 9 rings of spines called scalids - complete gut, but no circulatory system or nephridia ~ 100 species

36 Phylum Loricifera Head Thorax Abdomen


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